This invention relates to a system that facilitates authentication of genuine articles and discrimination of genuine articles from counterfeit articles. This invention relates more particularly to first order authentication, detection, discrimination, and recognition of indicia or taggants that become visible when they are excited by sources of invisible radiation, such as ultraviolet (UV) or infrared (IR) light sources. Specifically, the authentication is accomplished by human judgment through visual means by comparing an article with an applicable reference-standard sample-specimen provided with the apparatus and disposed to facilitate comparison.
The counterfeiting of articles of many kinds has become a serious problem worldwide causing great loss of revenues to legitimate business, individuals, and governments. One of the methods to protect the articles from counterfeiting is incorporation of special markings that are difficult to reproduce but that enable easy detection. Examples are articles that are tagged or marked with identification marks that are printed using normally invisible chemicals, such as UV- or IR-sensitive chemicals. (Throughout this description, the term xe2x80x9ctaggantsxe2x80x9d refers to materials or visible or invisible indicia included in or on an article to mark it for authentication. In order to avoid confusion with xe2x80x9cpurexe2x80x9d ultraviolet light sources that emit only ultraviolet light, those commonly available light sources that emit ultraviolet light and also emit some visible light will be referred to as xe2x80x9cblack lightxe2x80x9d sources.)
Counterfeiting, moreover, has produced articles with similar hidden identification marks that are so sophisticated that only high performance scanners and laboratory equipment can distinguish the counterfeit article from the genuine article. At the same time, counterfeiters using primitive methods, apparatus, and processes have produced some less valuable articles, such as food stamps, coupons, toys, etc. that will require first order authentication in the field. Since the articles in question do not command high value, it is often not practical to employ sophisticated apparatus in the first order authentication process. Instead, low-cost and reasonably reliable apparatus is preferred.
Many devices have been developed which can automatically determine authenticity of articles by detecting markings made with substances that are not normally visible in ordinary light, but become detectable by the devices when illuminated with non-visible radiation. U.S. Pat. No. 3,573,472 to Madalo discloses a label verification system in which each label to be verified is imaged onto a matrix of photocells, and an authentic label is imaged onto another matrix of photocells. Symbols on the labels preferably contain photoluminescent substances, and the matrix of photocells is provided with suitable filters, so that when the labels are illuminated with ultraviolet light, photocell responses are at a much higher degree of contrast. U.S. Pat. No. 4,146,792 to Stenzel et al. discloses paper secured against forgery and a device for checking the authenticity of such papers. The paper carries materials that fluoresce in the visible, ultraviolet, or infrared spectral range in characteristic emission spectra. The device includes a light source for exciting fluorescent substances, a condenser lens concentrating the light emitted by the paper, a narrow band interference filter, a focusing lens, and a series of photocells arranged in the focal plane of the focusing lens. The outputs of the photocells are fed to a preamplifier and then to a comparator, and outputs of photocells are compared to establish the authenticity of the paper. U.S. Pat. No. 4,277,774 to Fujii et al. discloses a currency discriminating apparatus that utilizes the presence of a light-emitting substance in a printed zone of the currency when irradiated with ultraviolet rays. The apparatus comprises an ultraviolet ray-emitting member, a photoelectric converter element, and a discriminating circuit for checking pattern signals. U.S. Pat. No. 4,558,224 to Gober discloses a counterfeit paper currency bill warning device that utilizes the characteristic fluorescence of genuine paper currency. In Gober""s device, an ultraviolet lamp illuminates the paper currency of unknown origin, and a sensor circuit responds to fluorescent radiation from the currency to give a signal to an indicator which displays an indication of the fluorescence of the unknown paper currency relative to the fluorescence of genuine paper currency. The sensor is a photoresistor and the indicator is a variable intensity light or a digital display.
U.S. Pat. Nos. 4,451,521 and 4,598,205 to Kaule et al. disclose security paper with authenticity features in the form of substances luminescing only in the invisible region of the optical spectrum. A corresponding test apparatus makes it possible to check the authenticity of the security paper in the presence of customers but unnoticed by them. The invisibility of the test signal and the authenticity signal are taken advantage of, and the test device is hidden behind a plate non-transmissive for visible light, which however is transmissive for the test signal and for the authenticity signal. U.S. Pat. No. 4,833,311 to Jalon discloses a security marking procedure, an apparatus to sense a security marking, and fiduciary documents provided with security markings utilizing rare-earth chelates consisting of at least two rare earths. The fluorescent wavelengths of the rare-earth chelates vary as functions of temperature.
U.S. Pat. No. 4,889,367 to Miller discloses a multi-readable information system which includes information in a machine-readable bar code and a different type of information that occupies the same field area of the substrate material, such as information in humanreadable symbology that is printed in at least a portion of the area occupied by the bar code. The bar code is printed in a first ink that can be read utilizing energy of a first wavelength and the human-readable symbols are printed in a second ink that can be read under illumination by a humanly visible wavelength. U.S. Pat. No. 5,414,258 to Liang discloses apparatus and methods for calibration of fluorescence detectors; the apparatus incorporates standard target elements comprising predetermined fluorescent substances with known emission spectra and either non-fluorescent substances or fluorescent substances with other known emission spectra.
Automated authentication systems for articles tagged with UV sensitive chemicals are well established, for example, the Angstrom Technologies Omni series UV scanners and systems. Similar systems are described in U.S. Pat. No. 4,642,526 to Hopkins, in U.S. Pat. Nos. 5,418,855, 5,548,106, 5,574,790 and 5,666,417 to Liang et al., and in U.S. Pat. No. 5,719,948 to Liang. These authentication systems prove to be accurate and fast in authentication without needing any human subjective judgment. They are commonly employed to differentiate valuable genuine articles from the counterfeit articles. However, they are also relatively expensive and sometimes cannot be justified for applications where the value of the articles in question is very low. Furthermore, in situations where not all articles have been tagged with the specialty chemicals, such as older passports, bank notes, and some credit cards, a fully automated system could give false readings if the articles are scanned automatically without human intervention. Similarly, a universal automated scanner for all credit cards or bank notes will be a challenging task because various credit cards and bank notes have different markings, with different taggants, and at different locations on the cards or notes.
PCT International Publication WO 97/06502 xe2x80x9cOptical Image Authenticatorxe2x80x9d by Atherton et al. describes an authentication system in which a light intensity pixel array is detected and compared with a reference pixel array to determine if each pixel is either good or bad. Authentication is done on the basis of the number of good/bad pixels or their ratio.
Several of the approaches in the prior art have addressed only individual currency standards in existence at the time of their invention, such as general broad-band fluorescence from paper stock, commonly known as background fluorescence, emitted by brightener or other substance used in the paper-making process. Any broad-band fluorescent ink can possibly trigger a detector of these types; for example, a mark that has fluorescent characteristics positioned anywhere on the currency or a simple stamp mark with fluorescent property. Therefore, such methods are not completely reliable.
The prior art generally does not describe solutions to the problem of how to authenticate the recently printed United States of America currency in which each denomination ($20, $50, $100 and the planned future $10 and $5 bills) has its own unique fluorescent xe2x80x9csecurity thread.xe2x80x9d Currencies of other nations, such as France and Switzerland, also have unique fluorescent features for each denomination of currency. Furthermore, the prior art does not address the method of authenticating other security features in the currency or in other articles that have security features other than fluorescent features.
Typically, desirable modern security features contain both visible and invisible means for enhanced counterfeit protection. The U.S. currency mentioned above has several security features visible under ordinary light characterized by wavelengths in the visible portion of the spectrum, in addition to its fluorescent features. For example, it has fine-line printing patterns in selected areas, a watermark, color-shifting ink in selected indicia, microprinting, Federal Reserve System indicia, etc. Many other currencies, such as those of Austria, Egypt, France, Germany, Italy, the Netherlands, and Switzerland, also have combinations of invisible and visible features, such as fluorescent paper, stripes, numerals, or threads, and a watermark visible in ordinary visible light. Therefore, it is desirable, under some situations, to have an authentication system that is more flexible and versatile even if it requires human judgment and even if it is less accurate and capable than an automatic system.
In many applications, it is desirable to have fast authentication capability of an article with visual means because the articles are not uniformly tagged for automated scanning such as U.S. currency $100, $50, or $20 bills, or credit cards, such as Visa, Master Charge, or American Express credit cards.
The commonly available black lights with some UV output and IR viewing scopes are simple to operate, have great flexibility and are of relatively low cost. Authentication of articles in question using only such apparatus is, however, completely dependent on subjective human judgment. Since counterfeiters can often imitate the taggant with a roughly similar chemical and printing, including printings by hand and rubber stamp, it will challenge a human examiner""s ability to distinguish counterfeit articles from the genuine articles. The relatively unreliable earlier authentication methods merely using black lights or IR viewing scopes alone have very limited practical value. It is therefore desirable to have an improved apparatus and methods suitable for first-order visual authentication.
An overall object of the invention is an authentication system that is low in cost and versatile but reliable to the first order. Portability, ease of operation, interchangeability of holders of the article to be authenticated (henceforth xe2x80x9carticle-under-testxe2x80x9d), and provisions for a reference-standard sample-specimen are other objects of this invention.
A system is provided for performing first order authentication of articles marked with indicia discernible in visible, ultraviolet, or infrared light or tagged with UV- or IR-sensitive chemicals. The first-order authentication system provides reliable visual authentication by providing for juxtaposition of the article-under-test with a known reference-standard sample-specimen, while the article-under-test is illuminated by a suitable source of radiation in the visible, ultraviolet, or infrared portions of the electromagnetic spectrum. Thus, the system facilitates comparison to differentiate a genuine article from a counterfeit article with first-order accuracy but at a substantially lower cost than that of automated authentication systems. Additionally, the system can be used in both portable and desk top embodiments. The system preferably has optional interchangeable holders for various articles-under-test as well as an optional interchangeable holder for various reference-standard sample-specimens. Some embodiments utilize structures incorporating split-image optics, superposed-image optics, and/or a blink-comparator.